Georadar
Et radargram fra en historisk begravelsesplads i Alabama, USA. Hyperboliske refleksioner (tilbagekastninger) indicerer tilbagekastende forhold under jordoverfladen, måske tilknyttede begravelser.
En georadar eller jordradar (kort GPR fra engelsk Ground Penetrating Radar) er et instrument beregnet til at undersøge strukturen i et fast legeme, fx i jorden.
Georadaren udsender elektromagnetiske bølger ned i jorden, hvorfra de tilbagekastes, hvis strukturen ændrer sig, fx hvis forskelligartede materialer findes strukturerede. Det strukturbillede, jordradaren finder, kan ses som et billede på en skærm og udprintes ved behov. Jordradarens evne til at trænge ned gennem jordlagene afhænger af disses beskaffenhed og af den benyttede antenne. En hovedregel er, at billedet forgroves ved stigende jorddybde.
Jordradaren har været i anvendelse blandt andet for at undersøge strukturen i Jellinghøjene, første gang i 1981 og igen i 1994.
Litteratur
- Harald Andersen: "Den tomme Jellinghøj" (Skalk 1994 nr. 2; s. 3-9)
|
Medier brugt på denne side
LINE21.jpg
Ground-penetrating radar depth section (profile) collected on an historic cemetery in Alabama, USA. Yellow arrows indicate very distinct reflections, probably associated with human burials. "hyperbolic" reflections, appearing as an inverted U, are typically associated with discrete objects. Less distinct hyperbolic reflections are indicated by red arrows. dashed blue lines indicate horizontal and sloping reflectors, probably bedrock. The many smaller reflections near the surface are likely to be caused by tree roots. Because of the nature of the site, subsurface testing was not conducted, but these interpretations are supported by surface indications (grave markers and depressions) and with line-to-line patterning within the GPR data.
Ground-penetrating radar depth section (profile) collected on an historic cemetery in Alabama, USA. Yellow arrows indicate very distinct reflections, probably associated with human burials. "hyperbolic" reflections, appearing as an inverted U, are typically associated with discrete objects. Less distinct hyperbolic reflections are indicated by red arrows. dashed blue lines indicate horizontal and sloping reflectors, probably bedrock. The many smaller reflections near the surface are likely to be caused by tree roots. Because of the nature of the site, subsurface testing was not conducted, but these interpretations are supported by surface indications (grave markers and depressions) and with line-to-line patterning within the GPR data.